JP4803675B2 - Optical fiber sensor type water pressure measuring device - Google Patents

Description

  The present invention relates to an optical fiber sensor water pressure measuring device to which an optical fiber sensor is applied.

2. Description of the Related Art Conventionally, a so-called FBG optical fiber sensor type water pressure measuring device that uses an optical fiber sensor, for example, measures the water pressure of groundwater is generally known.
However, in the so-called FBG optical fiber sensor type water pressure measuring device using the conventional optical fiber sensor, for example, for measuring the water pressure of groundwater, a temperature correction means with a simple configuration to remove distortion caused by temperature change. It was not a measuring device that adopted.
That is, in the past, correction of strain due to temperature change has been done by separately providing a strain detection component by temperature change that detects strain due to temperature change alone, but the cost of the device is increased accordingly. There is a problem that the water pressure measuring device itself becomes large (Japanese Patent Laid-Open No. 2003-28698).
JP 2003-28698 A

  However, in recent years, for example, a so-called FBG optical fiber sensor type water pressure measuring device that measures the water pressure of groundwater, for example, has adopted a simple means for removing the detection of strain caused by a change in temperature. There is a demand for the development of a so-called FBG optical fiber sensor type water pressure measuring device that uses, for example, an optical fiber sensor that can be formed at a low cost and measures the water pressure of groundwater.

Thus, the present invention was devised to address the above-described conventional problems, and employs a simple means capable of removing the detection of strain caused by a change in temperature in a so-called FBG optical fiber sensor type water pressure measuring device. Therefore, a so-called FBG optical fiber sensor type water pressure measurement device that can measure the water pressure of groundwater, for example, can measure the water pressure of groundwater using an optical fiber sensor that can be accurately measured at a low cost. It is intended to provide.

The optical fiber sensor type water pressure measuring device according to the present invention is:
A cylindrical water pressure measurement device main body having a hollow portion sealed inside, a water pressure detection unit provided in a lower opening of the cylindrical water pressure measurement device main body, and a water pressure value detected by the water pressure detection unit is fluctuated. A rocking width converting unit for converting into a moving width, a water pressure measuring unit capable of measuring the water pressure by the rocking width converted by the rocking width converting unit,
With
The water pressure detection unit, the swing conversion unit, and the water pressure measurement unit are disposed in the cylindrical water pressure measurement device main body,
The water pressure measuring unit has a cantilever holding member attached to the inner surface of the hollow portion in the vertical direction of the hollow portion, and swings up and down through the lower holding piece of the cantilever holding member. The swinging rod to be mounted is made swingable,
A first locking and fixing portion for locking and fixing the introduced optical fiber is formed on the lower holding piece side surface of the cantilever holding member, and an optical fiber is provided above the cantilever holding member. A second locking and fixing portion for locking and fixing
A rocking lock fixing portion for locking and fixing to the optical fiber between the first lock fixing portion and the second lock fixing portion is provided fixed to the rocking rod,
One FBG is provided between the first lock fixing portion and the rocking lock fixing portion, and between the second lock fixing portion and the rocking lock fixing portion, for detecting strain caused by the expansion and contraction of the optical fiber. Configured as a strain detector,
The strain due to the temperature change was measured by the strain detector, and only the strain due to the rocking change could be taken out.
It is characterized by
Or
The water pressure detection unit is provided at the lower end of the hollow portion in the cylindrical water pressure measuring device main body, and is formed as a water pressure receiving unit by a bellows-like or diaphragm-like expansion / contraction member that detects a value by converting a water pressure value into a swinging width. The
It is characterized by
Or
The swing conversion unit includes a swing rod that swings in conjunction with the swing of the water pressure receiving portion by a bellows-like or diaphragm-like elastic member, and a measurement width in which the swing width of the swing rod can be measured by the water pressure measuring unit. It is composed of a cantilever type conversion spring installed in contact with the tip of the rocking rod to convert to
It is characterized by
Or
The cantilever type conversion spring that is in contact with the tip of the swing rod is controlled to swing by a regulating bolt provided at an upper portion of the cantilever holding member.
It is characterized by
Or
The cantilever type conversion spring that is in contact with the tip of the oscillating rod can be changed in material or shape according to the level of water pressure to be measured.
It is characterized by
Or
The locking and fixing of the optical fiber is
An optical fiber having both ends of an optical fiber portion having an upper FBG locked between the second locking and fixing portion and the swinging locking and fixing portion and following the locked and fixed optical fiber portion After securing a predetermined length for each portion, the end portion of the optical fiber portion having the lower FBG which is locked and fixed to the swing lock fixing portion and continues from the locked optical fiber portion is said first engagement. Locking and fixing to the fixing part,
Alternatively, both end sides of the optical fiber portion having the lower FBG are locked and fixed between the swing lock fixing portion and the first lock fixing portion, and the optical fiber portion locked and fixed After securing a predetermined length for the subsequent optical fiber portion, the optical fiber portion is locked and fixed to the second locking and fixing portion, and the end portion of the optical fiber portion having the upper FBG extending from the locked and fixed optical fiber portion is shaken. Locked and fixed to the dynamic locking fixed part,
It is characterized by
Or
The second locking / fixing portion is connected to an adjustment bolt screwed in the vertical direction of the upper holding piece of the cantilever holding member, and the first locking / fixing portion and the second engagement are screwed in by the adjustment bolt. The tension of the optical fiber stretched between the fixing parts can be adjusted.
It is characterized by
Or
The swing lock fixing portion can be adjusted in the longitudinal position of the swing rod locking fixing portion by a swing rod adjusting bolt screwed in the vertical direction of the swing rod.
It is characterized by this.

  According to the optical fiber sensor type water pressure measuring device of the present invention, an optical fiber sensor which can adopt a simple means capable of removing detection of a strain caused by a change in temperature and can form an accurate water pressure at an inexpensive cost. For example, it is possible to provide a so-called FBG optical fiber sensor type water pressure measuring device that measures the water pressure of groundwater, for example.

Hereinafter, the present invention will be described based on the best mode for carrying out the invention shown in the drawings.
First, as understood from FIG. 1, an optical fiber sensor type water pressure measuring device 1 according to the present invention includes a cylindrical water pressure measuring device main body 3 having a hollow portion 2 therein, and the cylindrical water pressure measuring device main body 3. The water pressure detection unit 4 provided in the lower opening of the water pressure, the rocking width conversion unit 5 that converts the water pressure value detected by the water pressure detection unit 4 into a rocking width, and the rocking width conversion unit 5 And a water pressure measuring unit 6 that can measure the water pressure by the swinging width.

  The water pressure detector 4, the swing changer 5, and the water pressure measurement unit 6 are hermetically disposed in the hollow portion 2 of the cylindrical water pressure measurement device main body 3.

Here, first, a specific configuration of the water pressure detection unit 4 will be described.
As can be understood from the figure, the water pressure detecting unit 4 is formed as a water pressure receiving unit made of a bellows-like or diaphragm-like elastic member.
That is, a plurality of inlets 7 for introducing water such as groundwater are provided on the outer peripheral side of the cylindrical water pressure measuring device main body 3 on the lower side, and external water passes through the filter material 8 from the inlet 7. It is configured to pass through and be introduced into the apparatus main body 3.

Here, reference numeral 9 denotes a bellows-like cylindrical stretchable member formed of, for example, a resin that is stretchable in the vertical direction so that the water pressure of the introduced water is transmitted to the stretchable member 9. It is configured.
The lower end of the elastic member 9 is closed and divided into the inside of the elastic member 9, that is, the inside of the hollow portion 2 and the outside of the hollow portion 2.
Thus, a cantilever holding member 11 is attached to the inner surface of the hollow portion 2 in the vertical direction of the hollow portion 2 and penetrates the lower holding piece 12 of the cantilever holding member 11. A swinging rod 13 swinging up and down is attached so as to be swingable.
A cantilever type conversion spring 15 is provided on the tip 14 side of the swing bar 13 at a position above the cantilever holding member 11 and in contact with the tip of the swing bar. The material of the cantilever type conversion spring is not limited at all, but may be made of metal, for example, stainless steel. Further, it may be made of resin.

The shape, particularly the thickness, can be easily replaced with a cantilever type conversion spring 15 having a different thickness. Needless to say, it can be easily replaced with a different material.
Thus, the cantilever type conversion spring 15 is brought into contact with the tip of the swinging rod 13 in the vertical direction so as to convert the swinging width of the swinging rod into a measurement width measurable by a water pressure measuring unit 6 described later. It is configured to bend.

Here, the cantilever type conversion spring 15 uses a material whose shape and shape are changed according to the level of water pressure to be measured.
That is, in a place where it is predicted that the water pressure to be measured is high, the telescopic member 9 constituting the water pressure receiving portion 4 is contracted by the high water pressure, and the swinging width of the swinging rod 13 is increased. Therefore, the cantilever type conversion spring 15 is made of a material having a high Young's modulus, or the thickness is changed to change the shape so that the swing width can be measured by the FBG 20 described later.

Reference numeral 24 denotes a restriction bolt, and the restriction bolt 24 restricts bending of the cantilever type conversion spring 15 more than necessary.
Here, on the side surface of the lower holding piece 12 of the cantilever holding member 11, a first locking and fixing portion 17 for locking and fixing the optical fiber 16 introduced from the outside into the hollow portion 2 is formed. On the upper side of the cantilever holding member 11, a second locking / fixing portion 18 that locks and fixes the optical fiber 16 is also formed.

Further, between the first locking and fixing portion 17 and the second locking and fixing portion 18, a rocking and locking fixing portion 19 that is locked and fixed to the optical fiber 16 therebetween is fixed to the rocking rod 13. Is provided.
Then, the optical fiber 16 is expanded and contracted between the first locking / fixing portion 17 and the swing locking / fixing portion 19 and between the second locking / fixing portion 18 and the swing locking / fixing portion 19. FBGs 20 and 20 for detecting strain are respectively provided.

  As can be understood from the drawing, the second locking and fixing portion 19 is connected to an adjustment bolt 22 screwed in the vertical direction of the upper holding piece 21 of the cantilever holding member 11. By this screwing operation, the tension of the optical fiber 16 stretched between the first locking and fixing portion 17 and the second locking and fixing portion 19 can be adjusted.

In the figure, the adjusting bolt 22 and the regulating bolt 24 are integrally formed, but they may be formed separately.
In addition, the swing lock fixing portion 19 is also attached to the tip of the swing rod by a swing rod adjusting bolt 30 so as to be adjustable in the vertical direction of the swing rod 13. Therefore, when it is desired to adjust the position of the rocking lock fixing portion 19 in the longitudinal direction of the rocking rod 13, the rocking adjustment bolt 30 is used for adjustment.

  Note that when the above-described restriction bolt 24 is extended beyond the extension at which strain can be detected by the FBG 20, which will be described later, the cantilever type conversion spring 15 is pressed by the restriction bolt 24, and the upward swing of the rocking rod 13 is restricted. As already mentioned, it is possible to do this.

Here, with reference to FIG. 5, the attachment fixing state and the drawing state of the optical fiber 16 will be described.
It is well known that the plurality of FBGs 20 arranged in the longitudinal direction of the optical fiber 16 are arranged at predetermined intervals. This is because in the FBG based on so-called time division multiplexing, if a plurality of FBGs 20 are arranged too close to each other, it becomes impossible to detect distortion in each of the FBGs 20. Therefore, as shown in Example 1 and Example 2 in FIG. 5, a device was devised to maintain a predetermined interval between the two FBGs 20 and 20. That is, the introduced optical fiber 16 is fixed at three locations of the first locking and fixing portion 17, the second locking and fixing portion 18, and the swinging locking and fixing portion 19, and the adjustment bolt 22 (see FIG. 1) is operated. After adjusting the tension of the optical fiber 16, the swing lock fixing portion 19 is fixed to the swing rod 13 by the swing rod adjusting bolt 30.

Here, the optical fiber 16 is locked and fixed between the second locking fixing portion 18 and the swing locking fixing portion 19, and a predetermined length is secured as shown in Example 1 in FIG. It locks and fixes to the dynamic lock fixing part 19. The optical fiber 16 having the lower FBG 20 may be locked and fixed to the first locking and fixing portion 17.
Further, as shown in Example 2 in FIG. 5, the optical fiber 16 is locked and fixed between the swing lock fixing portion 19 and the first lock fixing portion 17, and a predetermined length is secured. 2 Locking and fixing to the locking fixing portion 18.
The optical fiber 16 having the upper FBG 20 may be configured to be locked and fixed to the swing lock fixing portion 19.
By adopting such a configuration, a predetermined long interval can be provided between the two FBGs 20 and 20, and the distortion can be reliably detected even by the FBG 20 by so-called time division multiplexing.

In Example 3 of FIG. 5, the predetermined length is not secured and the optical fiber 16 is locked and fixed. However, in this example, a WDM method of multiplexing at a so-called wavelength is employed. When the WDM method is employed, even if the arrangement is as in this example 3, the distortion of each FBG 20 and 20 can be sufficiently distinguished and detected.
Therefore, which type should be adopted may be determined in consideration of the actual installation location and installation status.

A closing member 25 that closes the upper opening is attached to the upper part of the cylindrical water pressure measuring device main body 3, and the introduction member that introduces the optical fiber 16 from the outside into the cylindrical water pressure measuring device main body 3. 26 and the optical fiber taking-in part 28 provided with the sending part 27 sending out from the inside to the outside of the cylindrical water pressure measuring device main body part 3 are attached.
Further, next to the optical fiber take-in portion 28, a reference atmospheric pressure introduction port 29 for introducing a reference 1 atmosphere of gas, for example, outside air, is formed in the hollow portion 2 of the cylindrical water pressure measuring device main body 3. For example, after a reference atmospheric pressure of 1 atm is introduced from the reference atmospheric pressure introduction port 29, it can be sealed.

The use state of the present invention will be described above.
An optical fiber 16 having two FBGs 20 and 20 attached thereto is introduced into the hollow portion 2, and the inside of the hollow portion 2 is set to a reference pressure of 1 atm. Thus, the optical fiber sensor water pressure measuring device 1 is configured, It is installed at a predetermined location where the water pressure should be detected.
Then, in order to detect the water pressure (the water pressure can be finally detected) at the installation location, the rocking rod 13 is formed by a water pressure receiving portion formed by the bellows-like cylindrical elastic member 9 or the like, that is, the water pressure detecting portion 4. Swings up and down.
That is, since the inside of the hollow part 2 of the cylindrical water pressure measuring device main body 3 is held at 1 atm, when the water pressure at the installation location is higher than 1 atm, the bellows-shaped water pressure detecting unit 4 is pressed, As shown in FIG. 2, the tubular elastic member 9 contracts.
Then, the swinging rod 13 whose lower end is fixed to the elastic member 9 swings upward. As the swing rod 13 swings upward, the swing lock fixing portion 19 swings upward. Then, the optical fiber 16 between the first locking / fixing portion 17 and the swinging locking / fixing portion 19 is pulled, and the FBG 20 installed therebetween detects the strain by this pulling.

Further, the optical fiber 16 between the rocking lock fixing portion 19 and the second lock fixing portion 18 is loosened, and the FBG 20 installed therebetween detects the strain.
As described above, the FBG 20 can detect strain due to the expansion and contraction of the optical fiber 16, but it can detect not only the strain due to the cause but also the strain due to a change in temperature.
Therefore, when detecting the water pressure accurately, in other words, detecting the water pressure that is the value to be finally detected, the strain due to the temperature change must be removed.

Conventionally, correction of strain due to temperature change has been done by separately providing a strain detection component based on temperature change that detects strain only due to temperature change. However, this increases the cost of the device. There was a problem that the water pressure measuring device itself would become large.
However, the present invention has solved such a problem. That is, when the strain values detected by the two FBGs 20 and 20 are described with reference to FIGS. 4 and 2, a strain εj generated by pulling the lower FBG 20 is obtained. However, the strain εj includes a strain εp due to a change in water pressure and εt due to a change in temperature.

Next, a strain εk due to loosening of the upper FBG 20 is obtained. As for this εk, a strain due to a change in water pressure occurs as -εp, contrary to the lower FBG 20. Further, εt is also generated as a strain representing a change in temperature.
Therefore, the strain can be determined from the temperature change from these equations (see equation (3) in FIG. 4).

FIG. 8 shows an example in which the present invention is applied to pore water pressure measurement.
It is said that there are two types of pore water pressure measuring devices: a pore water pressure measuring device for wall surfaces used for mountain walls and retaining walls, and a soil pore water pressure measuring device used by installing it in a borehole or in the ground. However, the measurement apparatus of the present invention can be applied to any case.
Referring to FIG. 8, when it is desired to measure the water pressure of the history layer 33 in the formation having the clay layer 32 below the gravel layer 31 and the history layer 33 below, the optical fiber sensor type water pressure according to the present invention. A measuring device can be used.

In this case, as shown in FIG. 8, the pore water pressure measuring device according to the present invention is inserted into the boring hole 34, fixed in the boring hole 34 by the packer 35, and used.

BRIEF DESCRIPTION OF THE DRAWINGS It is structure explanatory drawing (the 1) explaining schematic structure of this invention Example. FIG. 3 is a configuration explanatory diagram (part 2) illustrating a schematic configuration of an embodiment of the present invention. FIG. 3 is a configuration explanatory diagram (part 3) illustrating a schematic configuration of an embodiment of the present invention. It is an explanatory formula of "strain" acquired from two FBGs. It is explanatory drawing which shows the specific example by which an optical fiber is fixed by this invention. It is a schematic explanatory drawing explaining the specific example which applied this invention to the underground water pressure measurement. It is a schematic explanatory drawing explaining the specific example which applied this invention to river water pressure measurement. It is a schematic explanatory drawing explaining the specific example which applied this invention to the pore water pressure measurement.

DESCRIPTION OF SYMBOLS 1 Optical fiber sensor type water pressure measuring device 2 Hollow part 3 Cylindrical water pressure measuring device main body part 4 Water pressure detecting part 5 Oscillating conversion part 6 Water pressure measuring part 7 Inlet 8 Filter material 9 Extendable member 11 Holding member 12 Lower holding piece 13 Oscillating rod 14 oscillating rod tip 15 cantilever type conversion spring 16 optical fiber 17 first locking fixing portion 18 second locking fixing portion 19 swing locking fixing portion 20 FBG
21 Upper holding piece 22 Adjustment bolt 24 Restriction bolt 25 Closure member
26 Introducing section 27 Sending section 28 Optical fiber taking-in section 29 Reference pressure introducing port 30 Oscillating dredge adjusting bolt 31 Gravel layer 32 Clay layer 33 Gravel layer 34 Boring hole 35 Packer

Claims (8)

A cylindrical water pressure measurement device main body having a hollow portion sealed inside, a water pressure detection unit provided in a lower opening of the cylindrical water pressure measurement device main body, and a water pressure value detected by the water pressure detection unit is fluctuated. A rocking width converting unit for converting into a moving width, a water pressure measuring unit capable of measuring the water pressure by the rocking width converted by the rocking width converting unit,
With
The water pressure detection unit, the swing conversion unit, and the water pressure measurement unit are disposed in the cylindrical water pressure measurement device main body,
The water pressure measuring unit has a cantilever holding member attached to the inner surface of the hollow portion in the vertical direction of the hollow portion, and swings up and down through the lower holding piece of the cantilever holding member. The swinging rod to be mounted is made swingable,
A first locking and fixing portion for locking and fixing the introduced optical fiber is formed on the lower holding piece side surface of the cantilever holding member, and an optical fiber is provided above the cantilever holding member. A second locking and fixing portion for locking and fixing
A rocking lock fixing portion for locking and fixing to the optical fiber between the first lock fixing portion and the second lock fixing portion is provided fixed to the rocking rod,
One FBG is provided between the first lock fixing portion and the rocking lock fixing portion, and between the second lock fixing portion and the rocking lock fixing portion, for detecting strain caused by the expansion and contraction of the optical fiber. Configured as a strain detector,
The strain due to the temperature change was measured by the strain detector, and only the strain due to the rocking change could be taken out.
An optical fiber sensor type water pressure measuring device.
The water pressure detection unit is provided at the lower end of the hollow portion in the cylindrical water pressure measuring device main body, and is formed as a water pressure receiving unit by a bellows-like or diaphragm-like expansion / contraction member that detects a value by converting a water pressure value into a swinging width. The
The optical fiber sensor type water pressure measuring device according to claim 1.
The swing converting unit is configured to convert the swing rod that swings in conjunction with the swing of the water pressure receiving unit and the swing width of the swing rod into a measurement width that can be measured by the water pressure measuring unit. Consists of a cantilever-type conversion spring installed in contact with the tip of the heel,
The optical fiber sensor type water pressure measuring device according to claim 1 or 2, characterized by the above.
The cantilever type conversion spring that is in contact with the tip of the swing rod is controlled to swing by a regulating bolt provided at an upper portion of the cantilever holding member.
The optical fiber sensor type water pressure measuring device according to claim 1, 2, or 3.
The cantilever type conversion spring that is in contact with the tip of the oscillating rod can be changed in material or shape according to the level of water pressure to be measured.
The optical fiber sensor type water pressure measuring device according to claim 1, 2, 3, or 4.
The locking and fixing of the optical fiber is
An optical fiber having both ends of an optical fiber portion having an upper FBG locked between the second locking and fixing portion and the swinging locking and fixing portion and following the locked and fixed optical fiber portion After securing a predetermined length for each portion, the end portion of the optical fiber portion having the lower FBG which is locked and fixed to the swing lock fixing portion and continues from the locked optical fiber portion is said first engagement. Locking and fixing to the fixing part,
Alternatively, both end sides of the optical fiber portion having the lower FBG are locked and fixed between the swing lock fixing portion and the first lock fixing portion, and the optical fiber portion locked and fixed After securing a predetermined length for the subsequent optical fiber portion, the optical fiber portion is locked and fixed to the second locking and fixing portion, and the end portion of the optical fiber portion having the upper FBG extending from the locked and fixed optical fiber portion is shaken. Locked and fixed to the dynamic locking fixed part,
The optical fiber sensor type water pressure measuring device according to claim 1, 2, 3, 4, or 5.
The second locking / fixing portion is connected to an adjustment bolt screwed in the vertical direction of the upper holding piece of the cantilever holding member, and the first locking / fixing portion and the second engagement are screwed in by the adjustment bolt. The tension of the optical fiber stretched between the fixing parts can be adjusted.
The optical fiber sensor type water pressure measuring device according to claim 1, 2, 3, 4, 5, or 6 .
The swing lock fixing portion can be adjusted in the longitudinal position of the swing rod locking fixing portion by a swing rod adjusting bolt screwed in the vertical direction of the swing rod.
The optical fiber sensor type water pressure measuring device according to claim 1, 2, 3, 4, 5, 6, or 7 .

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